CBSE Class 11 Geography Chapter 9: Solar Radiation, Heat Balance and Temperature NCERT Solutions

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NCERT Solutions PDF Class 11 PDF

This chapter delves into the fundamental concepts of solar radiation, heat balance, and temperature as they relate to Physical Geography for Class 11 students. It explains how the sun's energy reaches the Earth, how it is distributed, and the factors influencing surface and atmospheric temperatures. The solutions cover topics like the direct overhead position of the sun on specific dates, variations in day length, the primary mechanisms heating the Earth's atmosphere, and the definitions of key terms such as insolation, albedo, isotherms, and annual temperature range. Understanding these principles is crucial for comprehending global climate patterns and weather phenomena. These NCERT Solutions provide clear explanations and step-by-step answers to help students grasp these essential geographical concepts, aiding in their exam preparation and overall understanding of Earth's climate system.

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Quick info

BoardCBSE
ClassClass 11
SubjectFundamental of Physical Geography
Session2026
LanguageEnglish
TypeNCERT Solutions
ChapterChapter 9

Chapter summary

Chapter 9 of the Fundamental of Physical Geography textbook focuses on Solar Radiation, Heat Balance, and Temperature. The NCERT Solutions provided here clarify the concepts of incoming solar radiation (insolation), its distribution, and the Earth's energy budget. It explains how factors like latitude, albedo, and terrestrial radiation influence temperature variations across the globe. The solutions also define important terms like isotherms and annual temperature range, crucial for understanding climate. This chapter's solutions are designed to help students understand the basic physics behind Earth's climate system.

Learning outcomes

  • Understand the concept of insolation and its variations.
  • Explain the factors affecting Earth's heat balance.
  • Define and differentiate between albedo, isotherms, and annual temperature range.
  • Analyze the reasons for temperature variations across different latitudes.
  • Identify the primary source of atmospheric heating.
  • Relate solar radiation to variations in weather and climate.

Topics covered

Paper topics

  • Solar Radiation
  • Insolation
  • Earth's Heat Balance
  • Terrestrial Radiation
  • Atmospheric Heating
  • Albedo
  • Isotherms
  • Annual Temperature Range
  • Latitude and Temperature
  • Day Length Variation
  • Subtropical High Temperatures
  • Equatorial Temperatures

Important topics

  • Insolation and its factors
  • Earth's Heat Budget
  • Role of Terrestrial Radiation in Atmospheric Heating
  • Albedo and its significance
  • Understanding Isotherms and Annual Range
  • Temperature variations with latitude

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Questions and Solutions

Multiple choice questions

(i) The sun is directly overhead at noon on 21st June at:

(a) The equator

(b) 23.5° S

(c) 23.5° N

(d) 66.5° N

Solution: The sun is directly overhead at the Tropic of Cancer, which is located at approximately 23.5° North latitude, on June 21st. This day marks the summer solstice in the Northern Hemisphere. Therefore, the correct option is (c).

(ii) In which one of the following cities, are the days the longest?

(a) Tiruvanantpuram

(b) Chandigarh

(c) Hyderabad

(d) Nagpur

Solution: The length of the day is influenced by latitude and the time of year. Generally, days are longer at higher latitudes during summer. Among the given Indian cities, Chandigarh is located at the northernmost latitude. Therefore, it experiences the longest days, particularly during the summer months.

(iii) The atmosphere is mainly heated by the:

(a) Short wave solar radiation

(b) Reflected solar radiation

(c) Long wave terrestrial radiation

(d) Scattered solar radiation

Solution: The Earth's surface absorbs short-wave solar radiation and re-radiates it as long-wave terrestrial radiation. This long-wave radiation is then absorbed by greenhouse gases in the atmosphere, which is the primary mechanism by which the atmosphere is heated.

(iv) Make correct pairs from the following two columns.

Column I:

  1. Insolation
  2. Albedo
  3. Isotherm
  4. Annual range

Column II:

  1. The incoming solar radiation
  2. The percentage of visible light reflected by an object
  3. The lines joining the places of equal temperature
  4. The difference between the mean temperature of the warmest and the coldest months
Solution: Here are the correct pairings between the terms in Column I and their definitions in Column II:
  1. Insolation matches with (a) The incoming solar radiation.
  2. Albedo matches with (b) The percentage of visible light reflected by an object.
  3. Isotherm matches with (c) The lines joining the places of equal temperature.
  4. Annual range matches with (d) The difference between the mean temperature of the warmest and the coldest months.

The main reason that the earth experiences highest temperatures in the subtropics in the northern hemisphere rather than at the equator is:

(a) Subtropical areas tend to have less cloud cover than equatorial areas.

(b) Subtropical areas have longer day hours in the summer than the equatorial.

(c) Subtropical areas have an enhanced "green house effect" compared to equatorial areas.

(d) Subtropical areas are nearer to the oceanic areas than the equatorial locations.

Solution: While the equator receives more direct solar radiation throughout the year, subtropical regions can experience higher average temperatures due to several factors. Option (a) highlights a key reason: subtropical areas often have less persistent cloud cover compared to the equatorial belt, allowing more solar radiation to reach the surface. Although subtropical areas do experience longer summer days, this is a seasonal effect. The greenhouse effect is present globally, and while it contributes to warming, it's not the primary reason for higher subtropical temperatures compared to the equator. Proximity to oceanic areas can moderate temperatures, but this isn't a universal characteristic that makes subtropics hotter than the equator.

Answer the following questions in about 30 words

How does the unequal distribution of heat over the planet earth in space and time cause variations in weather and climate?

Solution: The unequal distribution of solar radiation across the Earth, varying with latitude, season, and time of day, creates temperature gradients. These gradients drive atmospheric and oceanic circulation, leading to diverse weather patterns and distinct climatic zones worldwide.

Common mistakes

  • Confusing the direction of solar radiation with reflected radiation.
  • Misunderstanding the factors that cause variations in day length.
  • Incorrectly identifying the main source of atmospheric heating.
  • Difficulty in correctly pairing definitions with terms like insolation and albedo.

Revision tips

  • Focus on understanding the definitions of key terms like insolation, albedo, and isotherms.
  • Visualize the Earth's position relative to the sun on solstices and equinoxes.
  • Pay attention to the factors that cause temperature differences between land and sea, and between different latitudes.
  • Review the explanations for why certain locations experience longer days or higher temperatures.
  • Use the multiple-choice questions to test your understanding of basic concepts.

Practice MCQs

Q1. On which date is the sun directly overhead at 23.5° N latitude?

Q2. Which of the following cities experiences the longest days?

Q3. What is the primary source of heat for the Earth's atmosphere?

Q4. What does 'albedo' represent?

Q5. An isotherm is a line connecting places with:

Frequently asked questions

What is insolation?

Insolation refers to the incoming solar radiation that reaches the Earth's surface. It is the primary source of energy for Earth's climate system.

How does the atmosphere get heated?

The atmosphere is primarily heated by the long-wave terrestrial radiation emitted by the Earth's surface, which absorbs solar radiation.

What is the difference between insolation and albedo?

Insolation is the amount of solar radiation received by the Earth, while albedo is the percentage of that radiation which is reflected back into space by surfaces like clouds, ice, and land.

Why are temperatures higher in subtropics than at the equator sometimes?

While the equator receives more direct sunlight, subtropics can experience higher temperatures due to factors like less cloud cover, which allows more solar radiation to reach the surface.

What are isotherms?

Isotherms are lines drawn on a map connecting points that have the same average temperature over a given period.

How do these solutions help in exam preparation?

These solutions provide clear, rewritten answers to all questions, explaining concepts like solar radiation, heat balance, and temperature variations, which are crucial for understanding the chapter and performing well in exams.

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